Equalizing stub axle linkage suspension

ABSTRACT

A load-bearing apparatus for rail-mounted satellite tracking antennas, or other massive structures, which apparatus utilizes a four bar wheel-supporting linkage to maximize the area of contact between the supporting wheels and the rail, and hence to minimize the contact stresses between such wheels and rail.

United States Patent Schultz et al. 1451 Jan. 16, 1973 [54] EQUALIZING STUB AXLE LNKAGE [56] References Cited SUSPENSION UNITED STATES PATENTS [75] Inventors: Roger. T. Schultz, Los Altos; Jack 2 478 x87 8/1949 Germain 10S/180 /I'Siglra's tSAltfflylfmnd 1,256,558 2/1918 1-111d ..105/169 x i 3,302,589 2/1967 Williams... .....105/222 [73] Assignee: Philco Ford Corp., Philadelphia, Pa. l20,935 11/1871 Brown 5 m5/|69 l 348,467 8/1886 Kandeler... ..104/46 [22] Filedr March 27, 1970 981,131 1/1911 Spangen... .....105/180 x 2,644,697 7/1953 Peterson... ..280/80 [2l] Appl. N0.: 23,310 3,208,402 9/1965 Bingham .....105/133 450,386 4/1891 Hunt ..105/171 819,189 5/1906 Warner ..105/171 [52] U-S- Cl ..248/425, 16/31 R, 16/34, 2,874,647 2/1959 cand1in,1r.... .....105/171 104/1 R, 104/43, 104/83, 105/1 A, 105/136, 3,015,838 l/l962 Ulinski ..16/31 R 10S/171, 10S/180,105/199 5,105/218 R, 108/19, 108/138, 248/429, 280/80, 280/124 Primary Examiner-Arthur L. La Point A, 308/3, 343/763, 308/16 Assistant Examiner-Howard Beltran [5 l] Int. Cl ..B6lf 3/00, B6lj l/l2, HOlg 3/04 Attorney-Carl H. Synnestvedt [58] Field of Search ..74/471 R, 479; 104/35, 4l,

ABSTRACT A load-bearing apparatus for rail-mounted satellite tracking antennas, or other massive structures, which apparatus utilizes a four bar wheel-supporting linkage to maximize the area of contact between the supporting wheels and the rail, and hence to minimize the Contact stresses between such wheels and rail.

4 Claims, 6 Drawing Figures PATENIEDJM 1s ma.

SHEET 2 UF 2 INVENTORS EQUALIZING STUB AXL LINKAGE SUSPENSION BACKGROUND OF THE INVENTION This invention is concerned with the support of very large wheel-borne loads which are mounted for movement relative to a fixed supporting rail. Such wheelborne loads may, for example, comprise a large and massive antenna, such as the antenna systems used in the tracking of earth satellites.

In systems of this kind difficulties have been encountered due to relative misalignment between the support wheels and the rail. Any such misalignment interferes with the desired distribution of the load upon the rail, with consequent variations in the contact stresses. If a crowned rail is used misalignment is minimal, but there is only partial contact of wheel and rail and consequent high stress. If, alternatively, the rim of the wheel is cylindrical, and the rail is flat, the area of contact between the wheel and a properly aligned rail is at a maximum, with consequent minimization of stresses. However if the rail and wheel become misaligned for any reason, there is only partial contact of the wheel with the rail, with consequent higher stress levels for a given load than exist if contact takes place across the full width of the rail and wheel. Special problems have existed where the supported structure is driven, in azimuth, through the wheels. Attempts have been made to use compliant material between the wheel housing and the support structure, but the difficulties have persisted.

SUMMARY OF THE INVENTION It is the objective of our invention to eliminate previous difficulties. We accomplish this by interposing a four bar linkage between each wheel and the massive supported structure, the links of which are so dimensioned and associated that any relative movement between the contacting surfaces of the wheel and rail, in a direction tending to reduce the area of contact, causes a moment of unbalance causing certain links of the mechanism to pivot in a direction such as to move a free link, and the wheel carried thereby, in a direction to maximize the area of contact.

ln achieving this general objective, a base link is fixed to the load, a pair of swinging links are pivotally associated with spaced portions of said base link, and a fourth or free link is pivoted to said swinging links at free end portions of the latter. This free link includes means journalling the supporting wheel for rotation.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawings:

FIG. 1 is a perspective illustration ofa massive antenna structure of the kind with which the invention is concerned;

FIG. 2 is a detailed showing of a type of' wheel mounting known in the prior art and illustrating, on an exaggerated scale, a type of misalignment problem with which the invention is concerned;

FIG. 3 is a detailed elevational view, corresponding to FIG. 2, but illustrating the improved apparatus of our invention;

FIG. 4 is a schematic diagram of the four bar linkage embodied in the apparatus of FIG. 3;

FIG. 5 is view, partly in section, illustrating a motor drive arrangement of a type which may be used in conjunction with one or more ofthe driving wheels, and

FIG. 6 is a side elevation, on a reduced scale of apparatus shown in FIG. 3, the view being taken along the line 6-6 applied to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT With initial reference to FIG. l, there is illustrated a large tracking antenna structure 10, although it should be understood that the principles of the invention are applicable to structures of other types, for example, traveling cranes or other heavy machines which employ wheels and rails to support a massive moving structure.

Since the present invention is not concerned with the antenna system per se, or with the apparatus by which it is driven to effect adjustments in azimuth and elevation, detailed description of such antenna system is not required herein. For the purposes of an understanding of this invention, it is sufficient to point out that the antenna comprises a very large and massive dish 11 mounted upon a circular support structure 12, which may for example be of masonry. The dish is mounted through the agency of a plurality of wheel assemblies 13 (in this case three) riding upon a circular track, and pivoted about center support structure not shown. Applicants assignee corporation has developed a number of synchronous satellite tracking (SST) earth station antenna systems of this general kind, and in one embodiment the width of the dish is nearly l00 feet and the track diameter is 58 feet.

The track 14 comprises a steel rail set in or secured on the support structure l2 and defining a circle about which the wheels move in azimuth tracking of the antenna. Preferably, for reasons pointed out below, the track has a substantially fiat upper surface.

As indicated earlier in this description, difficulties have been encountered in the support of such large wheel-borne loads. The primary difficulties have to do with misalignment between the support wheels and the rail. Certain prior art apparatus illustrated in FIG. 2 illustrates the misalignment problem which can arise in support of such a massive structure and will assist in understanding the reason for the high stress condition which results. The conventional wheel mount shown in FIG. 2 comprises a yoke l5 fixed as at 16 to an antenna or other massive structure shown fragmentarily at 17. The yoke has bearing means 18 which journals a wheel 19 for rotation about an axis 20. Preferably such wheels are provided with a cylindrical or a conical periphery, it being possible to taper the wheel toward the center of rotation of the antenna, the degree of taper being limited by the angle at the center of rotation which a wheel of a certain size subtends.

When misalignment between the wheel axle and the rail surface occurs, as can result from twisting of the rail or movement of the rail bed, the result is a tendency to open a lateral gap between the surface of the rail and the wheel. This gap is shown in FIG. 2 at 2l, and has been referred to as the track tilt angle. In the past, efforts were made to accommodate such misalignment by the'use of a crowned rail as is shown in the figure. However a crowned rail, at best, permits only partial contact of the wheel with the rail as is represented in the drawing at 22 increasing the stress level. lf a flat rail Vis used the stress level is reduced, as long as no misalignment occurs, since there is broad contact between the wheel and the rail. This is the desired condition. However, it has been difficult to maintain in practice and objectionably high stresses result in the presence of track tilt such as is illustrated, exaggeratedly, in FIG. 2. As noted above attempts have been made to overcome this difficulty by introducing compliant material between the yoke l and the structure 17, but such attempts have not met with much success.

FIGS. 3, 4 and 6 illustrate the improved four bar wheel-supporting linkage of the present invention, which eliminates the alignment problems while permitting broad contact of the wheel across the top of a flat rail. A base link 23 is fixed to or formed as part of the load 24 in such a way as to define a line-of-centers 25. As viewed in FIG. 3, a pair of swinging links 26 and 27 are, respectively, pivoted to the base link at 28 and 29 and a fourth or free link 30 is pivoted to the swinging links at free end portions 3l and 32 of the latter, at points defining a second line-of-centers C. It will be understood that preferably', and as shown in FIG. 6, two identical pairs of swinging links support the wheel. These pairs, while comprised of individual links converging ltoward the rail (FIGS. 3 and 4), lie in parallel planes and each forms part of a separate four-bar struction will best be understood by comparing, in FIG.

6, the links 26and 27, of one pair, with the links 26'- and 27' of the other pair. The links of said one pair are pivoted at 28, 29 and 32, while the links of said other pair are similarly pivoted, as shown at 28' and 32. It will be understood that a part only of each of the links 27 and 27' is visible in FIG. 6, because of the plane of the section asshown in FIG. 3. The fourth link comprises a generally box-shaped yoke, and an intermediate portion of the legs thereof has bearing means 33 defining an axis 34. The wheel 3S is pivotally mounted by the bearings 33 for rotation about the axis 34. A flat rail 36 supports the wheel and its load and is, in turn, carried by suitable masonry structure 37.

The dimensioning and association of the links, see for example the links 23, 26, 27 and 30, shown in FIG. 3, are such that relative movement between the contacting edge portion of the wheel and a rail which is tending to become tilted, in a direction to produce misalignment represented at 38, automatically results in the linkage moving in such a way as to correct for the misalignment. It should be noted that FIG. 3 shows the linkage in the position which it occupies just before having moved to correct the track tilt misalignment represented at 38. After correction, the linkage lines of centers coincide with thev geometrical construction lines, as will be understood from comparison of FIGS. 3 and 4. Such movement results from the fact that the weight which the supported wheel carries produces a couple which causes the wheel to tilt, about the point or zone in contact with the rail, in a direction to reestablish broad contact between the wheel and the tilted rail. During such movement the wheel tilts in a direction to swing its face toward and into broad contact with the face of the rail. In this way use of the linkage results in maximizing the area of wheel contact with the rail and consequent minimizing of the stresses which would otherwise result from wheel-to-rail misalignment. The freedom provided in the linkage is such as to permit the links 26, 27 and 30 to make the corrective swinging movements which are necessitated by tilting of the wheel and/or the rail.

The way in which this linkage operates to achieve this result will become more clear by reference to FIG. 4 in which the linkage is shown schematically. The linkage is designed so that the intersection of the lines of centers of the swinging links 26 and 27, falls on the railwheel interface, as shown at 39, and is centered on the wheel rim when the track is level. As is apparent from inspection, if the fourth link 30 is short as compared with the base link, for small angular motions of the link 30 of the magnitude which result from tilting of the rail, the motion of the fourth link approximates true rotation about the center of contact 39 of wheel and rail. Thus the load line remains centered over the wheel face, the swinging links 26 and 27 are moved (compare the displacement of the line of centers of said links as shown in broken lines in FIG. 3), and the wheel is rotated about point 39 to a tilted position in which it remains in contact across the width of the rail. In this way, full rail-wheel contact and even load distribution is maintained throughout the range of misalignments which may be encountered in practice.

In an antenna support system of the kind with which the invention is concerned, it is known to drive the antenna around the track by the use of electric motors applied to one or more of the supporting wheels. As illustrated in the partly sectional showing of FIG. 5, motor drive apparatus 40 may be applied to one or. more of the wheel assemblies. As appears from FIG. 5 an electric motor 41 has associated therewith suitable reduction gearing 42 and the motor and gear assembly is fixedly associated with the yoke 30 (the fourth link) through the agency of a sleeve 43. Wheel 3S has a hub 44 formed integrally therewith, and this hub cooperates with bearings 33 in journalling the wheel for rotation. A spline connection 45 between the gear box and the hub completes the assembly. Since sleeve 43, and the parts carried thereby, comprise an assembly fixed to the tiltable yoke 30, this wheel driving assembly is free to move with the four bar linkage under the influence of wheel tilting movements resulting from contact of the wheel with a tilted rail.

While it is preferred to use four bar linkage in which the swinging links are of equal length, and the axis 34 of the wheel 35 is spaced well above the line of centers which passes through pivots 3l and 32, it is possible to revise the structure to some extent without departing from the principles of the invention. For example, it is possible to cause the axis 34 to approach coincidence with the track plane at the center of the circular track, which is desirable when using conical wheels.

In general, it is important that the distance between pivots 3l and 32, that is the length of the fourth or free link 30 (see FIG. 4), be short as compared with the fixed link 23, in order that the lines of centers of the swinging links fall on the center of the wheel face. It is also desirable that the lines of centers of each link be coplanar, to eliminate objectionable stresses -laterally of the linkage.

We claim:

1. ln apparatus for rotationally journalling a loadbearing wheel and for aligning the wheel with respect to an underlying support rail, mechanism providing for tilting of the wheel to maximize the area of contact between the wheel and such a rail and evenly distribute the load to minimize the contact stresses, said mechanism comprising four-bar linkage means disposed and configured to support the wheel in loadbearing relation between the load and such a rail, and including: a base link associated with the load and having means providing a pair of spaced pivots defining a line of centers extending transversely of the length of an associated rail; a pair of links each having one end pivotally associated with a corresponding one of said spaced pivots of said base link, the links of said pair depending from said base link and having free ends converging toward a point lying substantially in the region of such an associated rail, and each being mounted with freedom for swinging movements about a corresponding one of the base link pivots in a direction transverse the length of such a rail; a fourth link having spaced portions each of which is pivoted to a corresponding one of said swinging links in the region of the free ends of the latter, at points of pvotation defining a second line of centers extending transversely of the length of an associated rail and having an instant center of rotation lying in the region of the wheel-supporting surface of an associated rail; and means carried by said fourth link and journalling said wheel for rotation about an axis generally parallel to at least said second line of centers, said axis extending 'along a line spaced from and positioned between said two lines of centers.

2. Apparatus in accordance with claim l, and in which the distance between said swinging links along said second line of centers is small compared with the length of said base link.

3. Apparatus in accordance with claim l, and further characterized in that said swinging links are of equal length.

4. Apparatus in accordance with claim 1, and further characterized in that said fourth link comprises a generally box-shaped yoke having, in an intermediate portion of the legs thereof, means defining said axis, and in which apparatus said means journalling said wheel is carried by said yoke, and the end portions of the yoke are pivotally associated with the free ends of said swinging links. 

1. In apparatus for rotationally journalling a load-bearing wheel and for aligning the wheel with respect to an underlying support rail, mechanism providing for tilting of the wheel to maximize the area of contact between the wheel and such a rail and evenly distribute the load to minimize the contact stresses, said mechanism comprising four-bar linkage means disposed and configured to support the wheel in load-bearing relation between the load and such a rail, and including: a base link associated with the load and having means providing a pair of spaced pivots defining a line of centers extending transversely of the length of an associated rail; a pair of links each having one end pivotally associated with a corresponding one of said spaced pivots of said base link, the links of said pair depending from said base link and having free ends converging toward a point lying substantially in the region of such an associated rail, and each being mounted with freedom for swinging movements about a coRresponding one of the base link pivots in a direction transverse the length of such a rail; a fourth link having spaced portions each of which is pivoted to a corresponding one of said swinging links in the region of the free ends of the latter, at points of pivotation defining a second line of centers extending transversely of the length of an associated rail and having an instant center of rotation lying in the region of the wheelsupporting surface of an associated rail; and means carried by said fourth link and journalling said wheel for rotation about an axis generally parallel to at least said second line of centers, said axis extending along a line spaced from and positioned between said two lines of centers.
 2. Apparatus in accordance with claim 1, and in which the distance between said swinging links along said second line of centers is small compared with the length of said base link.
 3. Apparatus in accordance with claim 1, and further characterized in that said swinging links are of equal length.
 4. Apparatus in accordance with claim 1, and further characterized in that said fourth link comprises a generally box-shaped yoke having, in an intermediate portion of the legs thereof, means defining said axis, and in which apparatus said means journalling said wheel is carried by said yoke, and the end portions of the yoke are pivotally associated with the free ends of said swinging links. 